1. Field of the Invention
The present invention relates to an interchangeable-lens camera system such as a single-lens reflex digital camera or a compact digital camera, and to a method for controlling the camera system. The present invention is also applicable to an interchangeable-lens camera system such as a video camera or a mobile phone, and to a method for controlling the camera system.
2. Description of the Related Art
An interchangeable-lens digital camera of a single-lens reflex type, for example, which has an imaging device in a body unit thereof has a weakness that dust adheres to the surface of the imaging device during lens change and appears as an image on an image taken thereafter. In addition, the imaging device of such a camera is larger than that of a compact digital camera, making it difficult to reduce the camera size, and thus, such a camera is not suitable for casual shooting such as taking snapshots. On the other hand, such a camera has advantages that lens change allows use of various field angles and lens speeds and that using the large imaging device enables sensitive imaging with less big blur and noise.
Recently, a camera system no longer having the above problems but still having the above advantages has been proposed. Specifically, such a camera system includes various interchangeable lenses each having an imaging device with a size corresponding to the properties of the lens.
The above camera system having image devices with different sizes according to the lens properties, however, has problems which are not present in the conventional, interchangeable-lens digital camera of a single-lens reflex type having a single imaging device fixed inside the body of the camera.
For example, in the conventional interchangeable-lens camera system, items necessary for shooting (setting items), such as an ISO speed, a recording pixel count, a type of recorded image (JPEG or RAW data), an exposure metering scheme, and a focus drive mode, are set and saved through user operation on only the body unit of the camera system. However, in a camera system in which the imaging device is provided to the interchangeable lens, these setting items (setting information) need to be saved in both of the lens unit and the body unit.
If the interchangeable lens unit cannot save the setting information, imaging cannot be performed using setting information used in the last shooting after changing the interchangeable lens unit. For this reason, every time a new interchangeable lens unit is attached, various pieces of setting information for that interchangeable lens unit have to be set up for the new interchangeable lens unit. Japanese Patent Application Publication No. 2005-236773 discloses the following technique to address this problem. Specifically, the technique allows a destination for saving the setting information to be selected between the body unit and the interchangeable lens unit. Thereby, even when the interchangeable lens unit is detached from and then later coupled to the body unit, the interchangeable lens unit can be easily adapted to the intended use.
Depending on the purpose of using the camera, when the interchangeable lens unit is changed with another lens unit, a user may not want to use the same pieces of setting information, or, as described above, may want to use setting information different from that used for the previously-used interchangeable lens unit. The former case can be achieved by saving the setting information in the body unit. The latter case, on the other hand, requires the body unit to hold setting information different for each interchangeable lens unit, so that the body unit has to hold all the setting information corresponding to respective multiple interchangeable lens units. However, when there are many types of interchangeable lens units, it is not reasonable for the body unit to hold the setting information for a number of interchangeable lens units. This is because the number of types of interchangeable lens units may be infinite, whereas the body unit has a limited storage space. For this reason, to accomplish the purpose of saving setting information different for each interchangeable lens unit, it is desirable that the interchangeable lens units hold their corresponding setting information. Making the interchangeable lens units hold their setting information further allows multiple interchangeable lens units, even of the same type, to have setting information different according to the usage purpose and to be used according to the intended use.
In such a camera system in which interchangeable lens units each having an imaging device are attachable to and detachable from the body unit, each interchangeable lens unit performs differently depending on its type. Accordingly, there may arise the following problem when certain setting information saved in the body unit is to be used for multiple interchangeable lens units. Specifically, for example, the setting information may be applicable to an interchangeable lens unit of Type 1, but may not be applicable to an interchangeable lens unit of Type 2. To be more specific, some setting information may be applicable to (within the performance range of) the interchangeable lens unit of Type 1, but may not be applicable to (out of the performance range of) the interchangeable lens unit of Type 2. When the performance of the interchangeable lens unit attached and the setting information are incompatible, the setting of the interchangeable lens unit cannot be performed.
In some shooting situations or for some users, certain setting information should be used in common regardless of the interchangeable lens unit to attach, and certain setting information should be changed every time the interchange lens unit to attach is changed, in order to use setting information suitable for the interchangeable lens unit to use. Such a case requires a user to perform the setting of the setting information collectively, making it hard-to-use and cumbersome for the user.
As described above, the camera system in which interchangeable lens units each having an imaging device are attachable to and detachable from the body unit has specific problems in saving and reading setting information necessary for shooting.